E053 Denosumab-induced hypocalcaemia in patients with low eGFR: a case series

Abstract Background/Aims There are limited therapeutic options for treating patients with severe osteoporosis and chronic kidney disease, especially those with an estimated glomerular filtration rate (eGFR) of 30ml/min/1.732. These patients often have a very high risk of morbidity and mortality associated with a major osteoporotic fracture. Denosumab is effective at reducing the risk of osteoporotic fractures; however, it is associated with a risk of hypocalcaemia. We audited the risk of developing significant hypocalcaemia in patients with low eGFR taking denosumab for osteoporosis. Methods We present a small retrospective case series on patients with eGFR 30ml/min/1.732 who received denosumab 60mg by subcutaneous (SC) injection. Prior to administration, initial bloods, including bone profile, urea and electrolytes and vitamin D, were normal or corrected (vitamin D 50nmol/L). Blood monitoring of serum corrected calcium (cCa2+) was completed every 2 weeks for 6 weeks post denosumab injection (2, 4 and 6 weeks). All patients received high-dose Vitamin D3 as colecalciferol 20,000iu for 6 weeks (week 2, 4 and 6). Results We terminated the audit after treating seven female patients (age 74-95 years). There were six Caucasian and one South Asian patient. Six patients had a history of multiple fractures and one patient had been taking letrozole. The median baseline eGFR was 24 (4-31) ml/min/1.732, and mean baseline serum cCa2 + (at time of 1st injection) was 2.44 mmol/l (2.22-2.65). At 2 weeks, the mean serum cCa2+ was 2.14 mmol/l (1.54-2.51), at week 4, 2.24 mmol/l (1.90.2.51) and at week 6, 2.25 mmol/l (1.94-1.41). Two out of seven patients developed severe hypocalcaemia in week 2 (1.54 mmol/l and 1.62 mmol/l) with emergency hospitalisation to correct this. These patients had eGFR 4 ml/min/1.732 and eGFR 19ml/min/1.732, respectively. Both were asymptomatic and corrected with IV therapy. Two patients developed mild-moderate hypocalcaemia (1.90-2.10 mmol/l), one in week 4 and the other in week 6. There was no discernible trend between decreasing eGFR and decreasing serum cCa2+ levels across all weeks. Conclusion Treating elderly females with a low eGFR for osteoporosis with denosumab carries a significant risk of severe hypocalcaemia, which in turn can be life-threatening. The hypocalcaemia may be asymptomatic and, based on this audit, the risk is highest in patients with an eGFR 20ml/min/1.732. Disclosure R. Jarmal: None. S. Donnelly: None. V. Ramasamy: None. L.D. Williamson: None.